Of course I've pulled the disappearing act. But sometimes the disappearing act is also a tactical retreat. There are some women who are shopping for matching grave plots by the third date. Women with the rhetorical skills of a high-paid defense attorney who will argue with you when you politely tell them "This isn't working out." And there are also women who react to any rejection like a vampire catching a holy water balloon in the face. There are women out there who will make a dude's life living hell if he cuts it off. The drama isn't worth it. In those instances, I think the disappearing act is valid. If I've known you for three weeks, you don't get to freak out like we've been dating for six months.
To be fair, I've also disappeared because I was lazy or spineless or just a giant, greasy tool. But in all of those instances, I wouldn't say I was ever in a full relationship.
All of that is null and void, however. Because falling off the radar after a year of dating is sketchy. I won't excuse that. There are only a handful of scenarios I can come up with that would explain that. He went into Witness Protection. He's a closet hobo. He has a family. Or he's a thoughtless coward. If he had any sense of respect, he'd at least leave a note or something. But bailing without a word as to where he is or what he's doing after a year suggests to me he's with another woman, having a nervous breakdown, or he was a sniveling worm the entire year you were with him.